Instead of continuing the endless cycle of revisions, Espinoza took a different approach. According to Hertzfeld, Espinoza created a program that displayed all of the calculator's visual parameters through drop-down menus: line thickness, button sizes, background images, and more. When Jobs got to work, he spent about ten minutes tweaking the settings until he found a combination he liked.
The approach worked. By having direct control over the parameters rather than verbally stating his preferences, Jobs quickly arrived at a design that satisfied him. Hertzfeld notes that a few months later he implemented a calculator user interface using parameters selected by Jobs from that ten-minute session, while Donn Denman, another member of the Macintosh team, worked on the mathematical functions.
This ten-minute session resulted in the design of the calculator that shipped with the Mac in 1984 and has remained virtually unchanged throughout. MacOS 9when Apple discontinued this OS in 2001. Apple replaced it in Mac OS X with a new design that ends 17 years of using the calculator as the primary calculator interface for the Mac.
Why did it work
Espinosa's designer was an early example of what later became commonplace in software development: visual and parameterized design tools. In 1982, when most computers displayed monochrome text, the idea of allowing someone to fine-tune visual parameters using interactive controls without programming was quite prescient. Later tools such as HyperCard would formalize these kinds of ideas into a full-fledged visual application environment.
The primitive calculator design tool also revealed something about Jobs' management process. He knew what he wanted when he saw it, but may have had a hard time articulating it at times. By giving him the ability to directly manipulate, Espinoza completely solved this communication problem. Later returning to Apple in the late 1990s, Jobs famously insist evaluate products using them directly, rather than using ready-made PowerPoint demos or lists of specifications.
The duration of Jobs' ten-minute design session suggests that the approach worked. The calculator has survived nearly two decades of Mac OS updates, outliving many of the more complex interface elements. What started as a workaround has become one of the most simple yet robust Mac projects.
By the way, if you want to try out the original Mac OS calculator for yourself, you can run various older versions of the operating system in your browser thanks to Endless Poppy website.
